1. Field of the Invention
The present invention relates to an ultrasonic diagnostic apparatus for transmitting and receiving ultrasonic waves to perform imaging of organs and so on within a living body and generating ultrasonic images to be used for diagnoses. Furthermore, the present invention relates to a data analysis method and a data analysis program for performing analysis of data obtained in the ultrasonic diagnostic apparatus.
2. Description of a Related Art
In an ultrasonic diagnostic apparatus used for medical purposes, an ultrasonic probe is typically used to scan an object to be inspected with an ultrasonic beam formed by synthesizing plural ultrasonic waves and receive ultrasonic echoes reflected within the object, and thereby, image information on tissues of the object is obtained based on the intensity of the ultrasonic echoes. According to the ultrasonic diagnostic apparatus, a living body is acoustically measured by utilizing ultrasonic waves, and therefore, tissue properties of organs within the living body can be noninvasively diagnosed.
For example, the tissue property diagnosis of liver using the ultrasonic diagnostic apparatus enables early detection of cirrhosis. The cirrhosis refers to a symptom in which destruction and reproduction of liver cells are repeated and fibrillated tissues are increased within the liver and the liver is hardened and reduced. In this case, a feature appears in the intensity pattern of ultrasonic echoes in an ultrasonic image of the liver, and thus, the progression of the cirrhosis symptom can be visually confirmed.
Sometimes, the tissue property diagnosis using the ultrasonic diagnostic apparatus is made based on the pattern of speckles that appear due to mutual interference of echo signals reflected by a number of minute scatterers. For example, in the case where the liver is in the normal condition, the speckle pattern in the ultrasonic image is homogeneous. On the other hand, in the case where the liver is in the worsening cirrhosis symptom, the speckle pattern in the ultrasonic image is inhomogeneous. However, the visual evaluation largely depends on the experience of a person who makes a diagnosis, and therefore, quantitative evaluation is desired for homogeneousity of speckle pattern using the statistical nature of speckle pattern.
Naohisa KAMIYAMA et al., “Tissue Characterization Using Statistical Information from Ultrasound Echo Signals”, MEDICAL IMAGING TECHNOLOGY, Vol. 21, No. 2, March 2003, pp. 112-116 discloses a study on tissue property diagnosis using speckle patterns obtained by an ultrasonic diagnostic apparatus. According to KAMIYAMA et al., generally, the echo signal status from numerous random scatterers is expressed as a probability density distribution function and a liver condition can be diagnosed based on whether or not the probability density distribution function is distributed along a Rayleigh distribution. KAMIYAMA et al. also discloses that such a statistical technique is realized as an image filter.
Further, Yasutomo FUJII et al., “Texture Analysis with the New Method of Segments the Region of Interest into Multiple Layers for RF Amplitude Histogram Analysis in the Fibrous Liver of Rats”, J Med Ultrasonics, Vol. 28, No. 4, 2001, pp. J681-J691 discloses that, utilizing the fact that the histogram of enveloped-amplitude of RF (radio frequency) signals obtained from a homogeneous scattering medium resembles a Rayleigh distribution, a histogram analysis of enveloped-amplitude of RF signals is performed by focusing on the feature of the Rayleigh distribution function and segmenting ROI (Region of interest).
Furthermore, as a technology related to tissue property diagnosis using an ultrasonic diagnostic apparatus, Japanese Patent Application Publication JP-P2003-61964A discloses an ultrasonic diagnostic apparatus including analyzing and operating means for extracting a specific signal by using the statistical nature of intensity or amplification information of echo signals generated from a part of an object to be inspected, and display means for displaying a result extracted from the analyzing and operating means. According to the ultrasonic diagnostic apparatus, not only the progression of cirrhosis, but also a minute abnormal lesion in the homogeneous tissue structure can be observed by smoothing images by using the statistical nature of speckle pattern and extracting minute structures.
Further, Japanese Patent Application Publication JP-P2004-41617A discloses an ultrasonic diagnostic apparatus including image forming means for forming ultrasonic images based on echo data obtained by transmission and reception of ultrasonic waves, binarizing means for generating plural binarized images by binarizing the ultrasonic images while varying threshold levels, region counting means for performing labeling processing with respect to each binarized image to obtain the number of independent regions with high brightness or low brightness, and graph creating means for creating a speckle evaluation graph showing the number of independent regions with respect to each threshold level. According to the ultrasonic diagnostic apparatus, it is described that, utilizing the phenomenon that appearance of speckles or speckle pattern differs depending on tissue properties, tissue diagnoses can be made.
The tissue property diagnosis of liver, etc. may be made in a medical checkup, for example, and it is desirable that the evaluation result can be acquired in a short time period. Further, it is desirable for the person who makes a diagnosis or the person to be examined to easily understand the acquired evaluation result. However, the signal processing in the technology disclosed in the above documents is extremely complicated, and it is difficult to acquire the evaluation result in a short time period. Further, it is difficult for the persons to easily understand the evaluation result.